Tag Archives: urban heat island

Study Shows How Increased Reflectivity Can Save Lives

Researchers at the Georgia Institute of Technology recently published a report, in which they took a look at past heat waves in Phoenix, AZ, Philadelphia, PA and Atlanta, GA.

This study shows that by adding white roofs, reflective pavement and trees, cities can counteract temperature increases in urban areas and save lives. From an article byClimateWire

[T]he researchers modeled how the three cities would respond to a minimum green space ratio on land parcels, setting a floor for areas covered with grass, gardens or trees. Vegetation tends to have a cooling effect by circulating moisture in the air that draws away heat during evaporation. Tree canopies also provide cooling shade.

The team also modeled how Phoenix, Philadelphia and Atlanta would behave with more reflective streets, sidewalks, parking lots and rooftops. Higher reflectivity, or albedo, means the area absorbs less sunlight, thereby lowering the temperature.

Stone and his collaborators then overlaid a health impact model.  They found that combinations of increased vegetation and albedo could cut into projected increases in heat deaths, reducing them between 40 and 99 percent. “On average, we reduced the rate of increase by about 60 percent,” Stone said.

Groups like the Global Cool Cities Alliance are now trying to get cities to adopt these adaptation strategies, pitching them as a way to protect public health. However, it’s slow going, given that cities around the country address heat vulnerability differently, if at all.

You can find the full study HERE.

This report parallels a recent GCCA report, which looks at Baltimore MD, New York, NY, and Los Angeles, CA, and shows how reflective roofs and vegetation can cool air temperatures and save lives.

Note: Access to the ClimateWire articles is limited to subscribers.

Catch GCCA Executive Director Kurt Shickman on KCRW

Madeleine Brand, a reporter for NPR station KCRW in Santa Monica, California, noted that extreme heat is now the most deadly of weather-driven disasters.  She invited GCCA’s Executive Director, Kurt Shickman on her show to talk about the urban heat island effect, and Kurt explained how cool roofs can help cities cool down, conserve energy and save lives.  Kurt noted the many affordable color options available in today’s roofing marketplace.

They also discussed the new regulations in Los Angeles, which require white roofs on new commercial and residential buildings, as well as major roof rebuilds.

You can listen to the show here, and read more about efforts to bring down temperatures in Los Angeles with cool roofs,here.

LBNL Develops New Interactive Rooftop Reflectance Map

Scientists at the Lawrence Berkeley National Laboratory (LBNL) have created an interactive map that displays the solar reflectance (or albedo) of individual roofs in five major California cities – Bakersfield, Long Beach, Los Angeles, San Francisco, and San Jose.   This is the first time scientists have attempted to map the reflectivity of entire cities.

A white / high-albedo cool roof reflects 80% of the sun’s heat, decreasing solar heating of the building. This reduces the need for air conditioning and lowers energy bills. Cool roofs could also partially counter increased urban temperatures brought on by climate change.

This map allows users to zoom in on a specific rooftop to see how it compares to the albedo of a white roof, or other roofs in the city, and is designed to help cities develop policies that could lead to cooler cities.

Ronnen Levinson, head of LBNL’s Heat Island Group and Board Member of the Global Cool Cities Alliance says this new map can be a useful tool for cities:

To assess these potential benefits for a particular city, we need to measure the reflectance of its roofs with good spatial and spectral resolution.  Our map helps bring this into focus.

You can explore LBNL’s new interactive map HERE.

Study Links Climate Change to Hotter Urban Heat Islands

Cities are hot and getting hotter, thanks to global warming and the urban heat island effect.  With urbanization on the rise globally, extreme heat threatens human health, strains energy grids, and impacts global economies around the world.

Extreme heat is now ranked as the number one weather-related killer in the United States.  With over eighty percent of Americans now living in cities, urban heat islands and record high temperatures could cause serious health problems for hundreds of millions of people during the hottest months of the year.

Climate Central just released an analysis of government records for summer temperatures in 60 U.S. cities (1970 to date).  This study found that single-day heat island differences reached 27 degrees F in some cities, and that since 2004, at least 12 cities experienced 20 additional days a year above 90°F than surrounding rural areas.

This study also ranks the top ten urban heat islands in the United States.  Washington, DC ranks number 6 on this hit parade of urban heat.

Climate Central has prepared a useful interactive tool to help you learn more.

You can read more about the study here.

You can also read GCCA studies on heat health problems in Washington DC, and learn about strategies to lower urban temperatures and save lives.

U.S. Dept. of Energy Releases New Video on Cool Roofs

The U.S. Department of Energy just came out with this handy 2
minute video. It explains how the urban heat island effect
works, and shows how cool roofs are a simple and
economical way to cool things down in your city on a hot day.

This edition of Energy 101 takes a look at how switching to
a cool roof can save you money and benefit the environment.
Take a look:

To watch this on DOE’s Youtube channel, click here.

Catch GGCA’s Own Kurt Shickman on WAMU’s Metro Connection

Johnathan Wilson, environmental reporter for WAMU (a public radio station in Washington, DC) recently spoke with GCCA Executive Director, Kurt Shickman about the dangers of rising urban temperatures.  Kurt explained how reflective surfaces and increased vegetation help save lives in extreme heat events.

“We’ve found that on the average heat wave that lasts about four or five days, there’s about 10 additional deaths that wouldn’t have happened without that heat,” says Shickman.

Shickman and his colleagues at the Global Cool Cities Alliance estimate D.C. will save 20 lives over the next decade if it continues to lighten its flat rooftop surfaces and plant more vegetation.

GCCA released a report last October, in which we show that increasing reflective surfaces and vegetative cover in Washington, DC is a simple and cost-effective way to save lives during extreme heat events.

You can listen to today’s broadcast on WAMU HERE.

4 ways your city can be cooler next summer

This summer was a scorcher. Heat waves repeatedly struck the Midwest and South, sparing only sections of the Northeast. All of California is still in a drought. Cities were especially hot due to their concentration of buildings and human activity, a phenomenon called the urban heat island effect. At times, it may have felt impossible to beat the heat. Luckily, a recent report from ACEEE and the Global Cool Cities Alliance, Cool Policies for Cool Cities, shows how local governments enable communities to beat the heat before it starts. By employing the following cooling and energy-efficient practices before next summer, cities across North America can keep their cool:

Plant a Tree. A Chinese proverb says, “The best time to plant a tree was 20 years ago. The second best time is now.” Older trees with broad leaves and reaching branches provide a lot of shade for parks, pavements, homes, and offices, helping to keep them cool. They also clean the air and produce oxygen. Local governments often plant trees on city land, but did you know that many cities also provide free or discounted trees for planting on private land?

The Million Trees NYC program provides free trees to property owners, and runs a hotline for residents to call requesting a street tree be planted on their block.
Portland, Oregon offers a “Treebate” in the form of a $15-50 water bill credit to property owners who plant a tree on their land.
Grow Boston Greener offers a $2,500 grant competition to fund tree planting in selected neighborhoods.

Paint your roof. Dark-colored roofs trap and store heat. This heat radiates into the building, and doesn’t dissipate at night. Trapped heat is unpleasant and costly for residents who are forced to crank their AC, and is dangerous,sometimes deadly, for residents who don’t have access to air conditioning. A light-colored or reflective roof traps and stores considerably less heat. Cool roofs, for the same price as dark roofs, reflect the sun’s rays back out into the atmosphere. Recognizing the energy-efficient and publicly beneficial nature of cool roofs, some cities (and the entire State of California) require or encourage new and updated roofs to be reflective.

New and updated roofs in Los Angeles are required to meet a standard reflectiveness. To reduce the cost even further, LA’s Department of Water and Power offers a rebate of $0.20 to $0.30 per square foot.
St. Louis provides an innovative, low-cost financing option called Set the PACE St. Louis for residents replacing their traditional roof with one meeting a reflectiveness standard.

Replace dark pavement. Dark pavements also absorb, trap, and slowly release heat. You’ve experienced this running barefoot across a blacktop basketball court or parking lot. Light pavement, on the other hand, can be 50°-70°F cooler. Replacing dark pavement with vegetation also reduces the urban heat island effect. Grass and other permeable surfaces keep a city’s temperature down compared to pavement. As a bonus, they also filter stormwater. Cities have begun to encourage residents to paint parking lots, play areas, and alleyways with reflective coatings, or replace them with porous materials.

Chicago’s Green Alleys program transforms traditional alleyways into permeable ones. The program also empowers residents to derive more benefit from their green alleyways through pamphlets about landscaping and maintenance techniques.
Washington D.C.’s Riversmart programs enable individuals and communities to replace dark pavement and build green stormwater infrastructure through a series of grants and rebates.
Philadelphia offers stormwater bill credits to commercial property owners that install green stormwater infrastructure.

Vegetate your roof. A green roof eliminates the negative heat effects of a dark roof, and adds the benefits of oxygen exchange, amenity space, and opportunity for urban agriculture. Building a vegetated roof may seem like an expensive project, but many local governments are willing to share your costs.

Toronto, Ontario offers the Eco-Roof Incentive, a $75 per square meter rebate to help residents and businesses complete a green roof project.
Austin encourages green roofs by offering a variety of credits to developers for open space, parkland, and stormwater management. Density bonuses are also available.
Residents of Cincinnati may apply for a below-market-rate loan to install a vegetated roof. This is an effort through the Ohio EPA, the Metropolitan Sewer District of Greater Cincinnati, and the Cincinnati Office of Environmental & Sustainability.

Many local governments already do their part to reduce the urban heat island effect on their own properties, and some provide resources to help members of their communities do their part as well. Although the cities mentioned in this post (and many, many others!) are taking steps to reduce the urban heat island effect, every community can do more. An important driver of increasing urban heat island mitigation policies within a community is citizen demand. Strong private demand can help any of these cool technologies become standard market practice. Investing in cool technologies and buildings makes a community pleasant for all its inhabitants and visitors! Interested in learning more or cooling down your own city? First, check out the report to see what your city is doing to create a cool community. Next, participate in the programs that are available. If you aren’t impressed with what is offered, get involved and ask your city to keep its cool.


Originally posted on ACEEE’s blog: http://aceee.org/blog/2014/08/4-ways-your-city-can-be-cooler-next-s

Cities Now Contain Over Half the World’s Population

Hot summer days can often be sticky and miserable in an urban heat island.  Dark surfaces, lack of shade trees and climate-driven heat events mean higher summer temperatures and prolonged heat waves.  Add to that the growing population in many of the world’s mega-cities, and winter weather is looking better and better!

The United Nations Department of Economic and Social Affairs Population Division just released their World Urbanization Prospects report for 2014.  Over half the world’s population are now living in urban settings.  Some of the reports key facts:

Globally, more people live in urban areas than in rural areas, with 54 per cent of the world’s population residing in urban areas in 2014. In 1950, 30 per cent of the world’s population was urban, and by 2050, 66 per cent of the world’s population is projected to be urban.

Today, the most urbanized regions include Northern America (82 per cent living in urban areas in 2014), Latin America and the Caribbean (80 per cent), and Europe (73 per cent). In contrast, Africa and Asia remain mostly rural, with 40 and 48 percent of their respective populations living in urban areas. All regions are expected to urbanize further over the coming decades. Africa and Asia are urbanizing faster than the other regions and are projected to become 56 and 64 per cent urban, respectively, by 2050.

Close to half of the world’s urban dwellers reside in relatively small settlements of less than 500,000 inhabitants, while only around one in eight live in the 28 mega-cities with more than 10 million inhabitants.

Combine these population trends with rising world temperatures, and it’s clear that urban heat island mitigation is becoming more and more urgent.

Adapting to a Changing World

Our changing climate is impacting our lives.  From extreme heat to more severe storms, from droughts, famine and epidemics to wildfires and floods, we’re quickly learning that if we don’t mitigate and adapt, we’ll continue to pay the price.

According to a new report from the World Meteorological Organization, from 1970 to 2012, 8,835 disasters, 1.94 million deaths, and $2.4 trillion of economic losses were reported globally as a result of natural disasters such as droughts, extreme temperatures, floods, tropical cyclones and related health epidemics.  And as temperatures rise and more people move into more urban settings, these natural disasters are becoming more extreme and more deadly.

In the 1980s, droughts were among the world’s deadliest natural disasters.  Crop failures led to famine which caused hundreds of thousands of deaths in Northern Africa alone.  Thanks to new farming techniques, early warning systems, and better food distribution systems, droughts are killing fewer people around the world (adaptation works!).  But now another natural disaster is moving into the top spot: extreme heat.

From Brad Plumer at Vox.com:

But as droughts have become less deadly, heat waves seem to have become more so.  The WMO reports that heat waves were particularly lethal in the last decade, killing 72,000 people in Europe in 2003 and 55,000 people in Russia in 2010.

Here too, though, efforts are already underway to adapt.  In Europe, for instance, researchers have noted that many of the deaths in the 2003 heat wave occurred among the elderly with weak social networks and poor health care. (The heat wave followed right on the heels of a nasty flu outbreak.)  Better public-health infrastructure and monitoring might help here.

Likewise, scientists have observed that the urban heat island effect tends to exacerbate heat waves.  Because of all the buildings and cars and black pavement, cities tend to be even hotter than their surroundings. But there are ways to mitigate that.  One study found, for instance, that introducing more green spaces into a city could reduce the need for medical assistance during scorching heat waves by 50 percent.

Adapting to our changing world and bringing down urban temperatures will be more important as temperatures steadily continue to climb.  According to the latest data from NOAA, this June was the 38th consecutive June and 352nd consecutive month with a global temperature above the 20th century average.  This problem is not going away without determined mitigation action.

Meanwhile, to help communities deal with the health problems caused by climate-driven hazards, the U.S. Centers for Disease Control have put together a new set of guidelines.   Their recent report, “Assessing Health Vulnerability to Climate Change,” will help health departments identify their communities’ specific climate change-related health vulnerabilities.   It also provides guidance in the development of specific strategies to mitigate the health impacts of climate change.  The guide provides a five-step assessment process:

Determine the scope of the climate vulnerability assessment.

For these health outcomes, identify the known risk factors (e.g., socioeconomic factors, environmental factors, infrastructure, pre-existing health conditions).

Acquire information on health outcomes and associated risk factors at the smallest possible administrative unit.

Assess adaptive capacity in terms of the system’s ability to reduce hazardous exposure and cope with the health consequences resulting from the exposure.

Combine this information in a Geographic Information System (GIS) to identify communities and places that are vulnerable to disease or injury linked to the climate-related exposure.

Projections of Increased Urban Heat May Have Been Underestimated

They say that location is everything in real estate, and when it comes to measuring urban heat, where you collect your data will have an impact on the accuracy of your results.

A new study out of London illustrates just how important it is to take certain variables into account if you want to get an accurate measurement of urban heat.  In this case, tracking night time urban heat in a park full of trees means that previous measurements may have underestimated the urban heat island effect by as much as 45 percent.

From Pys.orgLondon heat boost underestimated:

Until now, the effect has been measured by calculating the difference between temperatures in St James’ Park in the city, and Wisley – a rural site just outside the M25.

But new research, published in the journalScience of the Total Environment, found night time temperatures in parks can be up to 4°C cooler than in the streets nearby.  So the St James’ Park measurements might have dramatically underestimated the urban heat island in the capital.

‘In the summer time, built-up areas effectively act like a storage heater,’ says Dr Kieron Doick of Forest Research, the research agency for the UK Forestry Commission, who led the research. ‘They store up heat during the day and release it at night.’

‘The extra heat can pose a real health risk, so it’s important to understand the impact that planning decisions have on temperatures in our cities.’

The study mentioned in this article can be found at: